There is a strange,bright green plant material growing in a mound right in the fork at the base of the trunk. It doesn't look like new leaves,because there are no stems. Is this some sort of parasite? The plant has been indoors for about 7 weeks. It hasn't happened on past citronella plants I've had. Thanks.
This is a signal that the soil pH might be getting a little on the alkaline side. I would add a little iron sulfate to the soil to bring that down some, and them some dolomitic lime to keep that stable for awhile. This is very odd, but it tends to happen in soils high in clay content- I.E. non potting soils. This will be easy to correct, and if you catch it this early will not cause any further issue.
Here is an article to refresh you on their care: https://www.gardeningknowhow.com/edible/herbs/scented-geranium/mosquito-citronella-geranium-plant.htm